Insects are continually exposed to an array of natural toxic plant chemicals and synthetic toxic insecticides that are used in the management of insects vectoring human and animal diseases and damaging crops. In a growing number of cases, the evolution of P450-mediated detoxification mechanisms have allowed insects to metabolize these compounds and enabled them to survive in the presence of high concentrations of plant toxins and insecticides. From the inception of synthetic insecticide usage in the 1940's, the acquisition of insecticide resistances in insects has increased to the point that they exist in over 500 species with many in species that significantly impact human health, such as the Anopheles mosquitoes that vector malarial parasites (estimated to kill as many as 3 million people per year) and the Aedes and Culex mosquitoes that vector yellow fever and West Nile disease. Our understanding of the molecular basis for these resistances and our ability to counteract these resistances depends on the development of comprehensive molecular models for insect P450s that couple theoretical modeling with protein expression and directed mutagenesis aimed at biochemically testing these models. The projects described are aimed at extending our P450 modeling and protein expression efforts to characterization of the catalytic sites in insecticide-metabolizing P450s in Drosophila, a model organism for the development of insecticide resistance, and in Anopheles, a significant vector for many human pathogens. At the level of molecular modeling, comparisons of these structures can provide information on the similarities (if any) of catalytic sites capable of handling insecticides, the differences that preclude some catalytic sites from binding and metabolizing insecticides and predictions on potential substrates and inhibitors for each protein. At the level of protein expression and high-throughput screening, profiling the range of compounds capable of binding to each catalytic site can define compounds potentially capable of interfering with insecticide metabolisms and, therefore, growth of pathogen-bearing insects resistant to current insecticides. The interdisciplinary mixture of molecular, biochemical and theoretical approaches used in this analysis are well beyond those available to most researchers in the field of insecticide resistance and provide us with significant potential for identifying inhibitors for P450s in mosquito species posing significant health risks as disease vectors. [unreadable] [unreadable]